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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Felipe Balbi <balbi@kernel.org>,
        Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Subject: [PATCH 5.10 284/299] usb: dwc3: gadget: Remove FS bInterval_m1 limitation
Date:   Mon, 10 May 2021 12:21:21 +0200
Message-Id: <20210510102014.303962446@linuxfoundation.org>
In-Reply-To: <20210510102004.821838356@linuxfoundation.org>
References: <20210510102004.821838356@linuxfoundation.org>
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From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

commit 3232a3ce55edfc0d7f8904543b4088a5339c2b2b upstream.

The programming guide incorrectly stated that the DCFG.bInterval_m1 must
be set to 0 when operating in fullspeed. There's no such limitation for
all IPs. See DWC_usb3x programming guide section 3.2.2.1.

Fixes: a1679af85b2a ("usb: dwc3: gadget: Fix setting of DEPCFG.bInterval_m1")
Cc: <stable@vger.kernel.org>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/5d4139ae89d810eb0a2d8577fb096fc88e87bfab.1618472454.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/dwc3/gadget.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -608,12 +608,14 @@ static int dwc3_gadget_set_ep_config(str
 		u8 bInterval_m1;
 
 		/*
-		 * Valid range for DEPCFG.bInterval_m1 is from 0 to 13, and it
-		 * must be set to 0 when the controller operates in full-speed.
+		 * Valid range for DEPCFG.bInterval_m1 is from 0 to 13.
+		 *
+		 * NOTE: The programming guide incorrectly stated bInterval_m1
+		 * must be set to 0 when operating in fullspeed. Internally the
+		 * controller does not have this limitation. See DWC_usb3x
+		 * programming guide section 3.2.2.1.
 		 */
 		bInterval_m1 = min_t(u8, desc->bInterval - 1, 13);
-		if (dwc->gadget->speed == USB_SPEED_FULL)
-			bInterval_m1 = 0;
 
 		if (usb_endpoint_type(desc) == USB_ENDPOINT_XFER_INT &&
 		    dwc->gadget->speed == USB_SPEED_FULL)